The Need for a Standardized Methodology for Quantitative Assessment of Natural and Anthropogenic Land Subsidence: The Agosta (Italy) Gas Field Case

In the last years, the advanced synthetic aperture radar (SAR) interferometry (InSAR) has proven its effectiveness in the assessment of ground gotion with millimetric accuracy. Its integrated use with traditional (in-situ) topographic height determination techniques, such as geometric leveling and Global Navigation Satellite System (GNSS), is consolidated in underground fluids extraction areas for detecting and monitoring land subsidence. Nevertheless, the lack of a specific standardized methodology does not allow for evaluating different results obtained from different types of analysis. Starting from the description of two independent estimations of land subsidence in the Agosta (Comacchio, Italy) area, where an environmental impact assessment procedure was carried out following a request for gas exploitation, this paper points out the need for a standardized methodology, focused on the in-situ calibration of InSAR data. This last purpose requires an adequately dense and homogeneous reference GNSS network. The in progress initiatives, at European and national level, aiming at providing a Copernicus Ground Motion service could offer the opportunity to structure a reliable and dedicated GNSS network, starting from the large amount of stations run by different institutions already existing in Italy.